@o_lampe
Did you ever 'measure' the length yourself?
I did some smallish calibration shapes (20mm I think) a very long time ago. At that size the problem is not visually recognizable and I would have considered deviations less than 1mm to be OK for my purposes.
It's only when I recently got into printing large center punching templates that I got to a place where accuracy matters enough for me to even notice the problem.
